Author Topic: stealing tech  (Read 17709 times)

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Offline birdman_express

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Re: stealing tech
« Reply #15 on: November 23, 2008, 01:52:43 am »
Some of these motors do see 8000 rpm for 30+ races a year.
Last for 2 full seasons, torn down over winter, refreshened,
and run two more seasons. Roller rockers and billet goodies.
Sounds like racing engines to me.

Now all that being said. Yall guys need your chance to
give this motor a test, race it in good competition,
and report your findings back here. Alot of the things you
are doing have been tried before, and the results vary.
We will be awaiting the results.

Marc
Marc Baker

ARC Dealer

Marc from ARC.... "Billet Billet"

Powered by a Full Bug E.C. 20HP Vanguard!!!!

Offline jake318

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Re: stealing tech
« Reply #16 on: November 23, 2008, 08:01:42 am »
 thanks Marc always had the intention to give results good or bad . In fact was going to give a result of the vaccume pumps that are on mowers (and scooters , have radical gy6 chinese AKA crap metal ergy motor)....toss them gravity has better flow at high rpm . the vacuum decreases at high rpm when you need gas the most . Most of you know this but thought a new guy might like the info. Jake

Offline Big daddy

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Re: stealing tech
« Reply #17 on: November 24, 2008, 04:59:55 pm »
What I was talking baout being "BIG" has to do with the dome size. I don't care how big the duration/lift is on your cam it will not force air into a space that an aluminum dome is occupying. If you go too long on the duration then you will have too much reversion from the carb. and that is just power wasted. You have to learn what George is telling you about the difference between singles and car engines is true. Some concepts and theory will cross over, but remember with a single you only have one cylinder doing the air movement, in a car engine there are 8 cylinders helping the air stream to move via the plenum area. The single must do this on its own. Think of it this way, think of opening a door to "RUN" into a room, the door opens you start running only to find a refigerator is just inside the doorway. You continue to run you smack into it, then you must pick yourself up and still get through the door. Now try doing the same thing, but this time there is a step stool inside the doorway.  Make sense now! That is what I mean by big is not always the best way to go when making the dome.
Bruce Litton

Offline jake318

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Re: stealing tech
« Reply #18 on: November 25, 2008, 03:17:09 am »
 Big i get the consept of the dome restricting flow but it doesnt stop flow.  ALL other  flathead racing uses domes ?  A Harley davidson  flathead is  relativly equal in displacement  even in bore and stoke dimensions with the briggs opposed twins. Ford flatheads bore and strokes are similar also . Mowers are the only motors leaving the compression ratios at 6.5:1 they are running 8:1 or 9:1 it would make sense that the gain of power of the higher compression is more than  increase of the increase of maximum flow. Time will tell ,  either way I will post the results  for everyone . jake
Ps I forgot to mention we are putting pockets in the  heads for valve lift  (Like the harley flatheads ) to give a channel for better fuel delivery.  Jake

Offline Big daddy

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Re: stealing tech
« Reply #19 on: November 25, 2008, 06:03:02 am »
I still don't think you are understanding. When the intake valve first opens, during the valve overlap and if you already have the motor up in its power band. The column of air in the manifold and carb should be moving on its own, now you slow it down because of restriction of flow, then it must regain speed and flow all during the intake stroke and nothing else. This is where you will loose volumetric efficiency in a big way. As far as putting pockets in the head for valve lift, well I think that would be a given. Pockets in my head are 0.250" larger than the valve diameter and 0.060" deeper for clearance above valves, I do not make them this size to decompress the engine, simply to increase flow around them and make sure they do not hit, anymore clearance than that and I have not increased flow but decompressed the engine for nothing, the dome idea will work BUT you cannot use a large dome especially in the area at the edge of the cylinder, the closer you get to the center line of the bore you can increase the size or height, but around the edges especially near the valves you would want the dome to blend to the same height as the block deck.
Bruce Litton

Offline schevy037

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Re: stealing tech
« Reply #20 on: November 25, 2008, 06:24:49 am »
If i read you right the reason for not wanting the edge of the dome higher is , it will be sticking up like a wall in front of the flow to stop it.
Rick Stohecker , opposed twin champ 2 years running .  River Rats LMRA . Northern Illinios

Offline jake318

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Re: stealing tech
« Reply #21 on: November 25, 2008, 06:58:59 am »
 Big I am always gratefull for info and you make make good point about the fuel velocity change. The high (or higher in this case being only 8-9:1) pistons are an experiment on 1 of 2 engines (opposed twins) so if  dies on the table all is not lost but I caant see how it would work well in one case and terrible in the next.  This is the Harley copy and  the next would be an actual dome design copying the eldebrock head( google eldebrock flathead you might find it interesting)   that design might not even be legal under uslma rules but at our local track anything goes and one guy is using a  SOHC motorcycle engine and that is :censored: me off. Hence the  new ideas. We got all the new suspension parts and tires available from ACME mower parts. if all else fails I will but an OHV engine  , but I definatly want to beat his motorcycle engine with a mower engine and a flathead would be icing on the cake . .....supercharged nitrous flathead ???? lol .... PS when you did your dome did you happen to test your compression results?

Offline Big daddy

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Re: stealing tech
« Reply #22 on: November 25, 2008, 01:07:13 pm »
When I ran a compression test on this engine I found I didn't have a real big increase in compression even though the dome filled the combustion chamber above the bore and the camshaft was advanced as far as I could go with it. It makes sense when you think about the air not able to get into the cylinder properly. Once you have the column of air moving anything that stops or even slows it down will have adverse results. To give you more background on the engine I used and its application, this was a tractor pulling engine. I had built an engine identical to this one the year before except with a flat top piston, the one with a flat top piston actually had more torque, the one with the dome piston would wind up a little more without a load on it but when loaded it would eventually fall on its face. I still have the piston I used as a paperweight. If you do decide to try it, my advice would be to use a dome that increases in height the closer you get to the center of the bore and blend it to the engine deck at the edge of the bore close to the valves, on the exhaust side you can be a little more aggressive with the climb from the edge of the bore, but the intake be more gentle with the blend as not to interrupt the air stream coming in.   Good luck.
Bruce Litton

Offline jake318

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Re: stealing tech
« Reply #23 on: November 27, 2008, 11:04:03 am »
Big, Went over flow with piston fabricator we are  putting in angle on valve pocket side of piston. ive never seen this done before but  I was thinking ... Why not take wedge inside of head out altogether and make a dome head? then you could use  with a dome  without impeading valve pocket.   What did you think of the Eldebrock flahead design ?

Offline Big daddy

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Re: stealing tech
« Reply #24 on: December 01, 2008, 07:24:02 am »
The Eldebrock Ford design looks more like an old flathead for a tractor. In "my opinion" when you chuck out the head in a semi hemispherical shape like that, then you must bring up the piston just to maintain the compression ration you started with, but now you have the issue of flame propagation across the head/piston surface. When we used domed pistons we used twin plugs on the head, one on each side of the dome, Their combustion chamber is not a bad one though. I have used a similar chamber design and had good results. Make your head to where it flows good, but don't over do it on the cylinder head with excessive clearance and cc. Then I would be more subtle in the area above the bore near the intake valve increasing towards the center of the piston, but you do not need to take the dome clear across the face of the piston. If you have good air flow in the cylinder head and make a dome that will not hamper the flow in any way you will make more power. Most of the domes I have seen go too far trying to eliminate space in the cc and end up costing more power than what is gained.
Bruce Litton

Offline Snowman18

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Re: stealing tech
« Reply #25 on: December 01, 2008, 09:26:20 pm »
All this talk about domes and you overlook the fact the dome isn't even in the air flow, why, because it's going down the cylinder. If you take your head and trace the outline of the gasket and flat part of the head over the cylinder, then cut it out and lay it on the block you will see the size of the window the air must flow through. Know that to raise compression you would have to make that window smaller, obviosly you don't want to do that because that would hinder flow, so the other way is to dome the piston and head artificially closing that window at the end of the compression stroke. Now the 11hp head is to thin to do that to even though it has nice flow characteristics it's just to thin. but the 12hp is thick enough. Also if the valves go high enough into pockets in the head it's like there not even there as far as the flow is concerned, and the time it takes to open them that far and close them can be calculated into the duration and shouldn't cause reverberation. My take on fire slots is, people are putting them in the wrong place, if you cut a slot above the piston you are lowering compression, a fire slot if used should be cut from the spark plug hole toward the center of the cylinder just long enough to blend into the ramp as the valve tends to shroud the plug with high lift cams.
Scott Nelson
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Offline jake318

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Re: stealing tech
« Reply #26 on: December 01, 2008, 11:41:52 pm »
  Hello all,   talking to the piston tech. the dome  doesnt get in the way if done correctly.  Lets face it   Old Harley Flatheads are gettting more hp per cubic inch  with a dome pistons than we are with these  mower engines with flow.  Its  racing engineers VS. old motorheads tinkering in a barn. Yes it cost more (650$ for 4 pistons) but as far as racing goes thats not breaking the bank. Jake

Offline Big daddy

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Re: stealing tech
« Reply #27 on: December 02, 2008, 12:32:49 pm »
If the dome is built properly it will not interfere with the flow if you back the dome away from the edge closest to the intake valve and slowly raise the dome towards the CL of the piston. If you fill the CC area above the cylinder bore then you will interfere with the incoming air. Take the head off of your motor when you have it on the bench. Take a degree wheel, find TDC, then turn the crank in engine rotation and when you get towards the end of the exhaust stroke you will find that your intake valve is opening up, note the location of your piston, if the valve is opening and the air stream is wanting to flow, now imagine you have a tall dome on top of your piston. Where is the air going to go? If you plan on starting and stopping the air stream using only the remaining 3/4" of your intake stroke then you will not have good volumeteric efficiency. Note the crank degrees that your valve spends in the lower "half" of the intake lift. This area is crucial for air flow in that your valve will spend more time in this range than any other. If you make the dome to where the air has a place to go while the piston is finishing the upstroke and starts the downstroke and the dome is not there to interfere because it is moving away and creating a void for the air then you will make good power. Proper shape and size of the dome is what the key is. Don't follow the notion that bigger is always better, here it is shape, area for incoming air -vs- piston location, and proper contouring to allow good laminar flow across the piston, but don't try to make a huge CC to accomodate the piston. Work with an existing CC design that works and manipulate the piston inside the CC area above the bore. You get the combinatin right and you will make power. unfortunately you will probably spend a ton of money getting the sweet spot figured out, that is why I have been using plain old flat tops since 1993. Spent a bunch to have the pistons made went out on a limb and tried it, learned a lot from it though. We still have one blank we may experiment with in a year or so, but for now just using the flatties!
Bruce Litton

Offline jake318

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Re: stealing tech
« Reply #28 on: December 03, 2008, 01:35:42 am »
 Big we have a second opposed that we are going to leave bone stock(beefed up rods  so they dont break)  with a litle nitrous oxside unit for a motorcycle.  Our track has a run what you brung motor policy. Either way , high tech,  high compression opposed twin or stock opposed with nitrous . I want to beat the guy that runs a 350cc motocycle engine. His mower doesnt turn that well(almost stock suspention) but he leaves everyone behind  down the straits including the OHV V-twins and wins the races We bought everthing  Mike Cupps sells at acme mower racing so the handling is covered. if we can match him down the strait we have him beat . To pass him down the strits would be icing on the cake.... Jake

Offline George Herrin

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Re: stealing tech
« Reply #29 on: December 03, 2008, 06:08:51 am »
OK guys nos and bikes and mowers don't mix here.
George Herrin #6
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